Refined estimation of time-varying baseline errors in airborne SAR interferometry

Abstract

The processing of airborne synthetic aperture radar (SAR) data requires a precise compensation of the deviations of the platform movement from a straight line. This is usually carried out by recording the trajectory with a high-precision navigation system and correcting them during SAR focusing. However, due to the lack of accuracy in current navigation systems, residual motion er- rors persist in the images. Such residual motion errors are mainly noticeable in repeat-pass systems, where they are causing time- varying baseline errors, visible as artefacts in the derived phase maps. In this letter, a refined method for the estimation of time- varying baseline errors is presented. An improved multisquint pro- cessing approach is used for obtaining robust estimates of higher order baseline errors over the entire scene, even if parts of the scene are heavily decorrelated. In a subsequent step, the proposed method incorporates an external digital elevation model for detec- tion of linear and constant components of the baseline error along azimuth. Calibration targets in the scene are not necessary.